The invention generally relates to pharmaceutical compositions, such as drug formulations present in a solid form for oral administration. More particularly, the invention relates to long-lasting sustained dosage compositions, and carriers and active ingredients in the compositions thereof, such as extended release drug compositions for oral controlled release dosage formulations containing a drug and a carrier material.
Drug delivery at a predetermined rate such that drug concentrations can be maintained at desired therapeutically effective levels over an extended period, has received a great deal of attention. Many known solid drug formulations are required to be taken orally three or four times a day. There is a need for oral formulations to be taken less often, such as once per day. In addition, there are other problems with undesired drug delivery rate. For example, various side effects are observed for immediate release drug formulations due to high drug concentrations released in the plasma or blood stream right after the intake of the drug.
Bupropion is a commonly used as an antidepressant drug. It is generally formulated from its salt derivatives, such as its hydrochloride salts. A commercial example is Wellbutrin®. However, it has been shown that immediate release formulations of bupropion hydrochloride can induce some severe side effects, such as seizures, high blood pressure, and severe allergic reactions. There is a need to prepare a new sustained release dosage form to reduce side effect problems.
Various approaches exist for preparing sustained or controlled release pharmaceutical formulations, such as various extended release formulations in tablet or capsule form. For example, one method of forming delayed or sustained release formulations includes coating the tablet with a release-retarding coating, or coating individual granules with such a coating, and compressing these coated granules into a tablet. Exemplary techniques involving sustained release solid preparations for bupropion hydrochloride in a matrix are described in U.S. Pat. Nos. 5,358,970 and 5,427,798. However, bupropion hydrochloride is unstable and the use of a stabilizer as described in the above two patents to stabilize the drug make the matrix methods is not very well suited.
Another example involves controlled release tablet formulations for bupropion hydrochloride by using a core containing bupropion hydrochloride and a coating of a mixture having a water-insoluble/water-permeable film-forming polymer, a pore-forming agent, and other excipients, as described in U.S. Pat. No. 4,687,660 and EP-A-0171457. However, the pore-forming agent renders the coating of the core non-uniform and the release rate of the tablet not stable. Other examples of controlled release tablets, as described in U.S. Pat. Nos. 6,096,341 and 6,143,327, require a core and a first coating to prepare a delayed release table, the first coating including a water-insoluble/water-permeable film-forming polymer, a plasticizer, and a water-soluble polymer. A second coating or an immediate release coating is then coated onto the delayed release tablet.
Therefore, there is a need for an improved controlled release formulation and method for preparing such a controlled release formulation.